MODELLING THE ENVIRONMENTAL IMPACTS OF TRAFFIC

Most of the road improvements in the past twenty years have been appraised using fixed matrix methods, with traffic growth being treated exogenously, though the possibility that major re- distributive effects might follow significant changes in access costs has always been recognised. The current methods are expected to provide good proxies for the more exact methods that could - in theory at least - be used under circumstances where congestion is severe, and trip making may be suppressed. This paper outlines and comments on appropriate methods for traffic and economic appraisal, and the sensitivity tests that may be required to confirm the robustness of the appraisal. The appraisal framework considered here is that of congested assignmenmt modelling, but the paper is primarily concerned with the interpretation of the more general principles of trunk road scheme appraisal set out in the Department of Transport's Traffic Appraisal Manual and the 1986 SACTRA (Standing Advisory Committee on Trunk Road Assessment) recommendations for urban appraisal than with the technical issues involved. The possible expansion of this framework is now being considered, however, and research and development is underway to explore the feasibility of modelling congestion effects within local trip end forecasting and to extend present congested assignment methods to handle a range of demand responses. Variable trip matrices methods have been somewhat neglected as they were not normally felt to be necessary, but the recent rapid traffic growth has re-opened interest in them. They pose some problems for the economic evaluation of schemes and link based methods have been devised to deal with these. Finally, the need for methods which allow consistent treatment of road decongestion benefits from both road and rail schemes has assumed greater importance in recent years, and has been an important factor in developing the current approach. (A) For the covering abstract of the seminar see IRRD 850684.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/isbn/0860502384
• Corporate Authors:

  PTRC Education and Research Services Limited

  Glenthorne House, Hammersmith Grove
  London W6OL9,   England 
• Authors:
  • Stark, D C
  • BROOME, M R
• Conference:
  • HIGHWAYS. PROCEEDINGS OF SEMINAR L HELD AT THE PTRC EUROPEAN TRANSPORT, HIGHWAYS AND PLANNING 19TH SUMMER ANNUAL MEETING, UNIVERSITY OF SUSSEX, SEPTEMBER 9-13, 1991. VOLUME P351
• Publication Date: 1991

Language

• English

Media Info

• Features: References;
• Pagination: p. 1-12

Subject/Index Terms

• TRT Terms: Conferences; Economics; Environment; Evaluation and assessment; Forecasting; Highways; Impact studies; Improvements; Mathematical models; Traffic flow
• Geographic Terms: United Kingdom
• ITRD Terms: 8525: Conference; 255: Economics; 2455: Environment; 9020: Evaluation (assessment); 132: Forecast; 2755: Highway; 9112: Impact study; 9108: Improvement; 6473: Mathematical model; 671: Traffic flow; 8119: United Kingdom
• Subject Areas: Economics; Highways;

Filing Info

• Accession Number: 00630604
• Record Type: Publication
• Source Agency: Transport Research Laboratory
• ISBN: 0-86050-238-4
• Files: ITRD, ATRI
• Created Date: Jul 1 1993 12:00AM